No perfect thyroid test. TSH is monitoring pituitary T3. Accurate only under ideal health. Free T4 is likely better test with TSH is the new state. Hypothyroid is a clinical diagnosis. (USC Rounds, 2017)

Extreme presentation of hypothyroidism. High mortality, life-threatening. Misleading name: usually not myxedema apparent, rarely in coma.

90% are women in winter months. Usually elderly > 60yo.

Clinical diagnosis. Altered (some big degree of AMS), hypothermia, body habitus for hypothyroidism. Usually bradycardia, hypotension, hypothermia. Stressor involved: infection (MCC), trauma, MI/CHF, surgery, medications, etc. Usually does not have a temperature and if has a normal temperature, have high suspicion for infection. Pleural effusions can be present. Look for thyroidectomy scar in altered patient. Usually hyponatremia. CPK almost always > 500.

Start with T4 over T3. Smooth/gradual rise, no high peaks and increased potential for arrhythmias/MI as T3. T3 though has advantage of quicker onset and no potential for decreased peripheral conversion (T4 to T3), though usually not recommended over T3. T4 500mcg or 200-400mcg (4mcg/kg) IV bolus, then 100mcg daily after that. Likely just stick with T4 only. If you’re going to give T3 (probably stay away from), give T3 5-20mcg IV bolus or consider giving very small bolus of T3 along with T4 if you really want to give T3 as well. Since body is converting T4 to T3, with giving a high dose of T4, the body will adjust to convert the appropriate amount to T3 so pretty safe to give high dose T4 (not T3 though). IV dose still takes around 12 hours before HR response.

Give antibiotics regardless of if theres an apparent infection initially since the myxedema coma masks many of the signs of infection.